M. Foale

Improvement of embryogenic callus production from coconut (Cocos nucifera L.) plumule explant

Magnolia macrophylla var. ashei is considered the most threatened Magnolia taxon in the USA (NatureServe 2015; Cicuzza et al. 2007), and its distribution is limited to ten counties in Florida (NatureServe, 2015). Indeed, approximately one half of the Magnoliaceae taxa are threatened worldwide according to the Red List of Magnoliaceae (IUCN, 2015). Tissue culture is an important tool to ensure the ex situ preservation of threatened Magnoliaceae when seed viability is low, and propagation from cuttings is difficult, as it is the case with this taxon (Riefler, 1984). Although some Magnoliaceae species and hybrids have been successfully micropropagated (Parris 2011; Zeng et al., 2002; Merkle and Wiecko, 1990), in vitro culture has not been widely utilized for conservation purposes for endangered species in this family. The proliferation of Magnolia shoots is difficult due to the oxidation of phenolic compounds during micropropagation (JunLi, 2007). Phloroglucinol (PG) has been recently shown to reduce browning in some woody plants (Kim et al., 2007; Agud et al., 2010), and it can act as a hormone synergist and as a precursor in the lignin biosynthesis pathway (Teixeira da Silva et al., 2013). An in vitro repository is being created at the Huntington Library, Art Collections and Botanical Gardens (San Marino, CA) for the ex situ conservation of Magnoliaceae biodiversity. Shoots (n=288) of Magnolia acrophylla var. ashei (provided by the Arnold Arboretum, USA) were cultured onto media with different levels of PG. The PG clearly prevented the blackening of the shoots after six weeks of culture, resulting in healthier plantlets when compared with the use of other antioxidants. The effect of salts composition and sugar concentration were evaluated to optimize shoot multiplication rate. The effect of PG is being tested now in several Magnolia spp. P-1001